Electrical submersible pumps are often used to pump fluids from hydrocarbon wells. An ESP normally includes a motor, a pump, and a seal section that reduces a pressure differential between well fluid on the exterior and dielectric lubricant in the motor interior. In many installations, the ESP secures to the lower end of a string of production tubing, made up of sections of pipe secured together with threaded ends. A power cable strapped alongside the production tubing extends from the surface to the motor.
For maintenance or replacement, normally, a workover rig is required to retrieve the ESP because the production tubing must be pulled. A conventional power cable cannot support its own weight in many wells, thus needs additional support if production tubing is not utilized. One technique involves placing the power cable within coiled tubing, which is a continuous length of metal tubing deployed from a reel. A coiled tubing injecting unit will lower the coiled tubing power cable and an inverted ESP down production tubing until an intake tube on the lower end of the pump stabs and seals into a polished bore receptacle in the production tubing. The pump discharges up an annular space in the production tubing surrounding the coiled tubing.
Many hydrocarbon bearing wells produce gas along with liquid, principally oil and water. The gas is detrimental to the efficiency of the most common type of pump, which is a centrifugal pump. A gas separator may be incorporated with the ESP in conventional installations with the ESP supported on production tubing. The gas separator may be various types, such as rotary or vortex, and it vents separated lighter components, such as gas, into the annulus between the production tubing and the casing in the well.